Spot Welding Conditions for Pure Titanium

Abstract

This paper deals with the spot welded pure titanium and problems in its welding.
The contact resistance was measured to select the optimum surface treatment operation. Both after degreasing and after wire brushing operation, it was in the range of 50-100 microhms but after pickling operation, it was decreased to the range of 20-30 microhms.
The formation of a spot weld is reflected in variation of voltage drop across the weld. The optimum welding schedule can be established by analysing the voltage drop variation.
Uniform weld size was found to be obtained without any care being taken to compensate for current shunting loss.
It was found that a variation in the electrode force over a considerable range did not affect the weld strengch, though the electrode force is an important factor deciding the amount of heat generated in the weld.
The weld strength of the spot weld was measured by tensile shear and normal tension test. The tensile shear strength can he expressed in simpler formula as a function of weld current and weld time.
(Tensile shear load S (kg/spot)=2400+8/5 I²⋅t⋅0^-5, Tensile shear strength S' (kg/mm²)=2.24.10⁵/I√t I=weld current, t: weld time
The weld strength tends to decrease as the weld current is increased.
The correlation of metallurgical structure of weld metal with weld strength has indicated that a welding schedule producing a fine grain weld metal is essential for securing optimum toughness.